U.S. patent application number 13/318366 was filed with the patent office on 2012-02-23 for coatings with small particles that effect bulk properties.
Invention is credited to Ganta Reddy, Jainagesh Sekhar.
Application Number | 20120045627 13/318366 |
Document ID | / |
Family ID | 43126418 |
Filed Date | 2012-02-23 |
United States Patent
Application |
20120045627 |
Kind Code |
A1 |
Sekhar; Jainagesh ; et
al. |
February 23, 2012 |
COATINGS WITH SMALL PARTICLES THAT EFFECT BULK PROPERTIES
Abstract
Durable interactive coatings which may be deposited on a
substrate which impact bulk properties i.e. bulk modifying
coatings, and a method and apparatus for producing them. Such
coatings can include a plurality of particles which adhere to the
substrate surface and/or other particles and include films. The
particles can be provided as one or more layers of nanoscale
particles having an average size of less than about 1000 nm, 800
nm, 500 nm, or 200 nm or 100 nm or less than 50 nm. Such bulk
modifying coatings can have a thickness that is less than about
5000 nm, 800 nm, 500 nm, or 250 nm or even 200 nm. Thicker coatings
or thinner coatings are provided depending on the potential field
thermodynamic interaction of the substrate and particles for bulk
property enhancement. Corresponding films are also provided.
Inventors: |
Sekhar; Jainagesh;
(Cincinnati, OH) ; Reddy; Ganta; (Cincinnati,
OH) |
Family ID: |
43126418 |
Appl. No.: |
13/318366 |
Filed: |
May 22, 2009 |
PCT Filed: |
May 22, 2009 |
PCT NO: |
PCT/US09/45068 |
371 Date: |
November 1, 2011 |
Current U.S.
Class: |
428/195.1 ;
118/620 |
Current CPC
Class: |
C23C 4/131 20160101;
C23C 4/11 20160101; Y10T 428/24802 20150115 |
Class at
Publication: |
428/195.1 ;
118/620 |
International
Class: |
B32B 3/00 20060101
B32B003/00; C23C 16/50 20060101 C23C016/50 |
Claims
1. A structure comprising: a substrate; and a coating applied to a
surface of the substrate; wherein the coating comprises a plurality
of particles, wherein each of the particles at least partially
adheres to the substrate or another one of the particles, wherein
at least one portion of the substrate is covered by the coating,
and wherein the at least one portion of bulk properties are
modified by the coating.
2. The structure according to claim 1 further comprising a bulk
modifying coating applied to a surface of the substrate wherein the
coating comprises a plurality of coating particles, wherein each of
the coating particles at least partially adheres to at least one of
the substrate or another one of the substrate particles, wherein at
least one portion of the substrate is covered by the coating, and
wherein at least one portion of the substrate is modified by the
coating and wherein the substrate is modified having said substrate
particles.
3. The structure according to claim 2 wherein at least one portion
of the bulk is modified, during or after the coating
application.
4. The structure according to claim 2 further comprising: a film;
wherein the film is at least partially adhered to each of the
coating particles of the coating.
5. The structure according to claim 1, wherein the coating is
substantially inorganic and wherein at least one of the particles
comprising the coating in comprised of a material that is glassy or
composite.
6. (canceled)
7. (canceled)
8. The structure according to claim 1, wherein at least a part of
the structure bulk comprises a region selected from the list
consisting of a cold worked region, a recovered region and a region
with grain boundaries wherein at least a part of the grain boundary
is modified by the coating.
9. (canceled)
10. (canceled)
11. The structure according to claim 1, wherein the composition of
a part of the bulk region is modified by at least one component of
the coating material.
12. The structure according to claim 1, wherein at least a part of
the grain boundary of a part of the bulk is modified by the
coating.
13. The structure according to claim 1, wherein the bulk
additionally comprises a adherent protective film on the substrate
or a polaron or a thermodynamic potential.
14. The structure according to claim 1, wherein the bulk contains
sessile dislocations or dislocation loops.
15. The structure according to claim 1, wherein the coating
comprises at least one of silicon carbide, siliconoxycarbide,
siliconoxynitrocarbide, ironsilicate, molybdenumcarbosilicide, or a
further carbide.
16. (canceled)
17. The structure according to claim 1, wherein the coating
comprises a grain or interface boundary.
18. The structure according to claim 1, wherein the bulk
modification includes a charge separation.
19. The structure according to claim 1, wherein the structure
comprises a sulfide, nickelide, aluminide, oxide, nitride,
oxycycarbide, oxynitrocarbide and combinations thereof.
20. (canceled)
21. (canceled)
22. The structure according to claim 1, wherein the coating
comprises a first layer and a second layer, wherein the first layer
has a first composition and the second layer has a second
composition, and wherein the second composition is different from
the first composition.
23. The structure according to claim 1, wherein the particles have
an average size of less than 20 nm to 1000 nm.
24. (canceled)
25. (canceled)
26. (canceled)
27. (canceled)
28. (canceled)
29. (canceled)
30. (canceled)
31. The structure according to claim 1, wherein the coating has a
thickness of less than 250 nm to 2000 nm.
32. (canceled)
33. (canceled)
34. (canceled)
35. (canceled)
37. The structure according to claim 1, wherein the coating
comprises a first layer and a second layer, wherein the first layer
has a first average particle size and the second layer has a second
average particle size, and wherein the second average particle size
is different from the first average particle size.
38. The structure according to claim 1, wherein the structure has a
form selected from the group consisting of a biological implant a
medical instrument, a household utensil, a transportation vehicle,
a lever, a knob, a key, a switch and a button.
39. (canceled)
40. (canceled)
41. (canceled)
42. (canceled)
43. (canceled)
44. An apparatus for providing a durable coating on a substrate,
comprising: at least one electrode; and an electrode arrangement
which is configured to produce an electrical arc at a distal end of
the electrode without the distal end of the electrode being in
proximity to an electrically grounded object, and which is further
configured to provide particles discharged from the arc onto the
substrate to form the bulk modifying coating, wherein a modified
bulk thickness is at least two time the thickness of the
coating.
45. (canceled)
Description
FIELD OF THE INVENTION
[0001] The present invention relates to materials having durably
adherent particulate which influence the bulk properties of a
material.
BACKGROUND
[0002] Surface coatings are normally used to improve surface
related properties of a material such as oxidation, corrosion or
surface wear. Should bulk properties be influenced by coatings,
then the possibility of enhancing several known alloys, including
metal, ceramics and polymers or even repairing alloys during field
operations may become possible leading to industrial and commercial
applications in a variety of fields ranging from biomedical
implants to boilers in ultra supercritical and supercritical energy
generation (herein referred to as USC) to electro ceramics to
transportation vehicles.
[0003] In certain industries like power generation there is a
strong energy and environmental impact with advanced materials
which can withstand higher temperatures or last longer in service.
In the energy industry each percentage increase in energy
efficiency gives rise to about an effective 2% reduction in
CO.sub.2 and SO.sub.2 emissions. The goal of improving the
efficiency of pulverized coal power plants has been pursued for
decades. The need for greater fuel efficiency and reduced
environmental impact is pushing utilities to USC conditions, i.e.
steam conditions of 760.degree. C. and 35 MPa. The long-term
fatigue, creep-strength, erosion and environmental resistance
requirements imposed by these conditions are rather severe and
clearly beyond the capacity of many currently used materials and
coatings. It is expected that maximum waterfall temperatures in
high efficiency units will approach 600-625.degree. C., with
super-/re-heater outlet temperatures expected to approach
.gtoreq.750.degree. C. with high heat flux. Material degradation
through steam oxidation, sulfidation, carburization, molten salt
and other corrosion mechanisms at these higher operating
temperatures may severely limit the serviceable lives of critical
components and is the primary impediment toward meeting the desired
fuel efficiency and environmental standards of these
next-generation power generation systems that include coal-fired
boilers, gas turbines, and solid oxide fuel cells (SOFCs).
[0004] Certain industries, such as the health care and medical
industry, may have a particular need for strong materials because
then the design can be lighter and section thicknesses smaller e.g.
in medical needles to food processing applications. In the
transportation industry, including land, sea, air, and space
vehicles, there may also be particular materials which need
advanced material properties with a further requirement for insitu
repair of such materials . . . . Protection from oxidation is
necessary for a wide variety of applications, from gas turbine
engines, steam turbines, chemical processing, petroleum refining,
to metal foil catalytic converters for automobiles. As the LHV
(lower heating value) is improved (from 40% to more than 50%), a
one percent increase in efficiency reduces by two percent, specific
emissions such as CO.sub.2, NOx, SOx and particulate matters.
Improvements are possible with an increase in the temperature and
pressure of boilers. Such boilers can be used in coal plants to
nuclear installations. Supercritical and ultra supercritical power
plants are highly efficient plants with best available pollution
control technology. Such boilers are `green` because they reduce
existing pollution levels by burning less coal per megawatt-hour
produced. There is a significant thrust in this direction--several
installations are now using USC boilers. Power plants are coming-up
with this state-of-the-art technology. As environment legislations
are becoming more stringent, adopting this cleaner technology could
benefit immensely in all respect. Protection against erosion is
particularly important for boiler materials such as T11. It is not
just enough to have a better surface but also to have better bulk
properties which can enhance the overall erosion and fatigue.
[0005] PCT/US2006/060621 and PCT/US2007/085564 discuss such
coatings, the disclosure of which is incorporated by reference
herein. The coatings and surfaces discussed in these two PCT's were
thought to influence surface properties, such as emissivity,
surface wear, antimicrobial, reflectivity, etc and thus enhance
durability but were not necessarily expected to influence bulk
properties of the substrate. In particular it has never been
anticipated that that a nanocoating will provide significant
improvement to bulk properties such as fatigue resistance, bulk
creep or erosion over time or wear resistance over time which
require bulk material properties to be considered or improved.
However surface fatigue crack initiation which is a surface
phenomenon can have been thought to be influenced by coatings. In
this specification we discuss coatings that influence much more
than a surface property namely bulk properties. A surface is a two
dimensional object whereas a bulk region has a third dimension
(three dimensional object) generally with a thickness at least
greater than the coating thickness. The interface between a coating
and a surface could be diffuse or sharp i.e. localized to a few
atomic layers or just one atomic layer. The word nano is commonly
used to signify 10.sup.-9 (most often used with meter as the length
unit).
[0006] The particle materials and coatings as described herein can
be durable because the morphology of the deposited particles (e.g.,
their approximate size, degree of porosity or interconnectedness,
etc.) may be essentially retained during exposure to high
temperatures, mechanical forces, chemicals, cyclic conditions of
fields etc. A high specific surface area may persist in such
particulate coatings and materials, even if some amount of oxide or
other reactive compound may form thereon, because of the presence
of the initial microscopic or nanoscale particles or from frozen in
dissipative waves created during the application process or Landau
waves, which can all influence the growth rate of such compounds at
least in the initial stages of growth. There are a particular class
of applications which invoke properties like fatigue, low crack
propagation rate, charge retention (e.g. capacitors),
semiconductors, superconductors, resistors, electro ceramics,
pizieoceramics, bioimplants (e.g. for bones, spine, valves, hip
etc.), electrodes for electrolysis including large electrolysis
like aluminum electrowinning, and smaller size electrodes used
batteries, multibarrier electronics (e.g. NPN, N and P junctions),
where, in particular the bulk material is required to be influenced
and controlled. In general, if a thermodynamic potential is induced
or modified by the particulate coating, then depending on the
strength and distance of the potential field, the bulk properties
are influenced. The particulates structure of the coating jointly
with the bulk including the modified substrate can thus interact
and produce bulk properties which are different from the uncoated
state. Sometimes the differences may be significant and sometimes
smaller based on the nature of interaction. Thermodynamic
potentials can be pressure (stress), electrical, thermal, magnetic,
electromotive, mass based, interface energies (like grain boundary
energy), chemical potential, energy gradient potential, free energy
or even polarons (several types), photonic or phonon fields,
dissipative patterns such as chemical oscillations and all the
possible interactions between fields including non periodic
oscillations.
[0007] Metal deformation on a surface by forging, welding, shot
peening or laser shot peening are known to modify some bulk
properties (non chemical) but these processes do not include
particle coating on the substrate. Coatings provide valuable
protection for surfaces as has for example been noted in
PCT/US2006/060621 and PCT/US2007/085564. In particular the use of
nanocoatings has not been anticipated to modify bulk structure
properties. Sometimes it is difficult to directly measure a
property. A noticeable change of microstructure is an indication of
the property change. Articles in transportation (e.g. jet engines
parts, automobile parts, steam turbines, nuclear use, space or
underwater use etc.), biological implants, household (e.g. knobs,
utensils, keys necklaces, switches, buttons etc.), in the energy
sector are possible with this invention. Other components for
example in energy production or storage such as chimneys,
scrubbers, electrostatic precipitators, cleaning systems, igniters,
ignition chambers, fluid (gas and liquid) delivery systems, water
pipes, clean water systems and tubes, hydraulic systems requiring
corrosion resistance and systems used in sequestering SO2, CO2 or
other gasses may benefit from this invention. The build of gunk
(residue e.g salts) in water tubes may be reduced because of the
bulk potential along with surface potential interactions that this
invention enables.
[0008] For some of the reasons outlined above a durable coating
which also impacts bulk properties is desirable. The film could be
a consequence of the particles, by itself or a feature that is
created by the bulk modifying particles, or from the modified bulk
or substrate. The particles could be attached to any of the other
features or penetrate the surface as also discussed in the
examples. Further, there may be a need to provide such materials
and coatings which are easy and relatively inexpensive to produce,
and which may be applied to a broad variety of substrates. Further
there may be a need for such coatings to be nanosized or comprise
of nanoparticles. In addition, there may be a need for such
coatings which can be applied to objects that are already in use or
that are in need of repair, for example boilers and heat exchangers
or tubes which may see hot erosion or corrosion over a long period
of usage. Boiler and heat exchanger is a term used interchangeably
in this application.
SUMMARY OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0009] The exemplary embodiments of methods and materials according
to the present invention can provide one or more durable coating
layers of closely spaced, but partially separated (e.g., not fully
sintered) small particles on a substrate which also influence bulk
properties. For example, such particles may have an average size
that may be less than about 1000 nm, less than about 800 nm, or
preferably less than about 500 nm, or preferably less than about
200 nm or more preferably less than 100 nm. The particles may have
a shape that is approximately, spherical, cylindrical, acicular,
tubular or a mixture of these geometries. Such coatings can have a
thickness that is less than about 5000 nm, or preferably less than
about 800 nm, or less than about 500 nm. Thicker coatings may also
be provided. For example, a coating of small particles may be
provided on a substrate using a single-sided electrode arrangement,
which can include a power generator, a Pi circuit or equivalent
circuit, and an electrode. The power generator can be a
high-frequency generator. The electrode materials as well as the
particles may be those described for example in PCT/US2006/060621
and PCT/US2007/085564. The use of metals, semiconductors,
phosphides, aluminides, nitrides, borides, sulfides, oxides,
metalloids and the various organic materials used for engineering
and general surface properties use are considered wherever they may
be bulk modifying. Ceramic materials are also fully considered
including PZT and electro ceramic materials. Defect structures with
non equilibrium and non-stoichiometric chemistries are anticipated
also, These and other objects, features and advantages of the
present invention will become apparent upon reading the following
detailed description of embodiments of the invention, when taken in
conjunction with the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Further objects, features and advantages of the invention
will become apparent from the following detailed description taken
in conjunction with the accompanying figures showing illustrative
embodiments of the invention, in which:
[0011] FIG. 1 is an illustration of an exemplary apparatus which
may be used to produce materials in accordance with certain
exemplary embodiments of the present invention;
[0012] FIG. 2 is an illustration of the exemplary apparatus which
may be used to produce coatings on large substrates in accordance
with other exemplary embodiments of the present invention;
[0013] FIG. 3 is an illustration of the exemplary apparatus which
may be used to produce coatings in accordance with further
exemplary embodiments of the present invention;
[0014] FIG. 4 is an illustration of the exemplary apparatus which
may be used to produce coatings in accordance with additional
exemplary embodiments of the present invention;
[0015] FIG. 5 is an exemplary image of an exemplary coating
provided by a scanning electron microscope ("SEM") in accordance
with certain exemplary embodiments of the present invention on a
common household plastic.
[0016] FIG. 6 is another exemplary image SEM image of a further
exemplary coating in accordance with further exemplary embodiments
of the present invention;
[0017] FIG. 7 is an exemplary image of an exemplary coating
provided by a scanning electron microscope ("SEM") in accordance
with certain exemplary embodiments of the present invention;
[0018] FIG. 8 is another exemplary SEM image of a further exemplary
coating in accordance with further exemplary embodiments of the
present invention;
[0019] FIG. 9 is another exemplary SEM image of a further exemplary
coating in accordance with further exemplary embodiments of the
present invention;
[0020] FIG. 10 is another exemplary SEM image of a further
exemplary coating in accordance with further exemplary embodiments
of the present invention;
[0021] FIG. 11 is an another exemplary SEM image of a further
exemplary coating in accordance with further exemplary embodiments
of the present invention;
[0022] FIG. 12: Oxidation plot (weight gain vs. time) of CCA617 in
steam at 750.degree. C. for 100 hours with and without embodiments
of the invention. The resolution and possible experimental errors
are in the order of 0.1 mg/cm.sup.2. The difference noted because
of the invention is substantially higher than any identified
resolution or experimental errors;
[0023] FIG. 13: Oxidation of (weight gain vs. time), with and
without embodiments of this invention, for S304H steel in steam at
700.degree. C. for 100 hours. The resolution and possible
experimental errors are in the order of 0.1 mg/cm.sup.2. The
difference noted because of the invention is substantially higher
than any identified resolution or experimental error;
[0024] FIG. 14: Oxidation of T92 steel in steam at 650.degree. C.
for 100 hours;
[0025] FIG. 15a. Coated CCA617 oxidized in steam at 750 C for 100
hours. SE (secondary electron image), of surface (top) and BSE
(backscattered image) of cross-section (bottom) micrographs.
Smaller thickness of the oxide layer (in this case a part of the
film) is noted compared with the uncoated. XRD analysis of the
oxidized surface showed the presence of Cr.sub.2O.sub.3 containing
Si and the FCC matrix;
[0026] FIG. 15b. Uncoated CCA617 oxidized in steam at 750 C for 100
hours. SE of surface (top) and BSE of cross-section (bottom)
micrographs. Larger thickness of the oxide layer (film) is noted
compared to the coated sample. XRD analysis of the oxidized surface
showed the presence of Cr.sub.2O.sub.3 and the FCC matrix;
[0027] FIG. 16a. Sample S11-5T: Coated Super304H steel oxidized in
steam at 700 C for 100 hours. SE of surface (top) and BSE of
cross-section (bottom) micrographs. Smaller thickness of the film
is noted compared with the uncoated. XRD analysis of the oxidized
surface showed the presence of Cr.sub.2O.sub.3 containing Si, (Fe,
Cr, Mn)O.sub.4 and the FCC matrix;
[0028] FIG. 16b. Sample C4: Uncoated Super304H steel oxidized in
steam at 700 C for 100 hours. SE of surface (top) and BSE of
cross-section (bottom) micrographs. Larger thickness of the film is
noted compared to the coated sample. XRD analysis of the oxidized
surface showed the presence of Cr.sub.2O.sub.3, (Fe, Cr, Mn)O.sub.4
and the FCC matrix;
[0029] FIG. 17a. Sample T1-5T: Coated T92 steel oxidized in steam
at 650 C for 100 hours. SE of surface (top) and BSE of
cross-section (bottom) micrographs. Finer oxide particles and much
smaller thickness of the film are noted compared with the uncoated
17b. XRD analysis of the oxidized surface showed the presence of
Cr.sub.2O.sub.3 containing Si, Fe.sub.2O.sub.3 and the BCC matrix
but with a different microstructure that 17(b);
[0030] FIG. 17b. Sample T2: Uncoated T92 steel oxidized in steam at
650 C for 100 hours.
[0031] SE of surface (top) and BSE of cross-section (bottom)
micrographs. Coarser oxide particles and much larger thickness of
the film are noted compared to the coated sample. XRD analysis of
the oxidized surface showed the presence of Cr.sub.2O.sub.3
containing Si, Fe.sub.2O.sub.3 and the BCC matrix but with a
different microstructure than 17(a);
[0032] FIG. 18: Comparative Static Air Oxidation of the CCA617
alloy, S304H steel, and T92 steel tube coupons with and without the
embodiments of the invention for 500 hours at 700 C, 700 C and 650
C respectively;
[0033] FIG. 19: Static Air Oxidation of the CCA617 alloy, S304H
steel, and T92 steel tube coupons for 500 hours at 700 C, 700 C and
650 C respectively illustrating benefits of the invention for
educed greenhouse emissions and energy usage;
[0034] FIG. 20a. Sample C7-5T: Coated CCA617 oxidized in air at 700
C for 500 hours. SE of surface (top) and BSE of cross-section
(bottom) micrographs. Oxide and film layer thinner compared with
the uncoated sample;
[0035] FIG. 20b. Sample C8: Uncoated CCA617 oxidized in air at 700
C for 500 hours. SE of surface (top) and BSE cross-section (bottom)
micrographs. Oxide and film layer thicker compared with the coated
sample;
[0036] FIG. 21a. Sample C9-5T: Coated CCA617 oxidized in air at 700
C for 1000 hours showcasing an embodiment of the invention when
compared to 21b;
[0037] FIG. 21b. Sample C10: Uncoated CCA617 oxidized in air at 700
C for 1000 hours. BSE micrograph of sample cross-section. Oxide
layer thicker compared with the coated sample;
[0038] FIG. 22a. Sample T5-5T: Coated T92 steel oxidized in air at
650 C for 1000 hours. BSE micrographs of sample cross-section.
Oxide layer thinner compared with the uncoated and number of grain
boundary or grain interior bright reflections is very different
when compared to 22b;
[0039] FIG. 22b. Sample T6: Uncoated T92 steel oxidized in air at
650 C for 1000 hours. BSE micrograph of sample cross-section;
[0040] Throughout the drawings, the same reference numerals and
characters, unless otherwise stated, are used to denote like
features, elements, components, or portions of the illustrated
embodiments. Moreover, while the present invention will now be
described in detail with reference to the figures, it is done so in
connection with the illustrative embodiments and is not limited by
the particular embodiments illustrated in the figures.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
[0041] Exemplary embodiments of the present invention on a variety
of substrates are discussed below. Such coatings can include, e.g.,
microscopic and/or nanoscale particles of certain materials which
may be strongly bonded to a substrate and/or to each other and
provide for bulk changes. The coatings may be porous or otherwise
not fully sintered or densified.
[0042] Such coatings may be created by very-strong electrochemical
decomposition processes (which unfortunately could passivate most
of the time) or such coatings may be applied using exemplary
techniques described, e.g., in U.S. patent application Ser. No.
11/098,474 and International Patent Application No. PCT/US06/60621
and PCT/US2007/085564, the entire disclosures of which are
incorporated herein by reference in their entireties. These will be
referred to as enhanced coating techniques or methods for
application of bulk modifying coating. Such exemplary techniques
which may be used to provide coatings of small particles are
described in more detail herein, and can be used to provide
coatings or materials which surprisingly exhibit changes in bulk
properties. An exemplary apparatus 100 which can be used to produce
bulk modifying coatings and surfaces in accordance with exemplary
embodiments of the present invention is shown in FIG. 1. Such
exemplary apparatus 100 can be configured to produce an electrical
arc or discharge 8 at a distal end of an electrode 2, where the arc
or discharge 8 can be produced without the distal end of the
electrode 2 being in proximity to an electrically grounded
object.
[0043] For example, the exemplary apparatus 100 can be based on a
one-sided electrode arrangement which may be configured to deposit
particles on a substrate or other surface. Such exemplary apparatus
100 can include, e.g., a high-frequency electrical generator or
power source 1, a conductive coil 3 which may be provided as a
coiled tube, and can be formed, e.g., using copper or another
conductive material, and an electrode 2 which can be formed of or
include a material to be deposited as at least part of an coating.
The electrode 2 may be conductive or semi conductive. Capacitors 4,
5, 6 can be provided in an electrical communication with the
conductive coil 3, which may exhibit electrically inductive
properties. For example, capacitors 4, 5, 6 and coil 3 may together
form a conventional Pi circuit, or exhibit electrical behavior
similar to such circuit. A carrier gas 7 may also be provided
adjacent to the electrode 2. When the exemplary apparatus 100 is
operated, an electrical arc or discharge 8 may be produced near a
distal end of the electrode 2, and ionic particles 9 may be emitted
from the electrode 2. Such particles can be expelled onto a nearby
substrate and may adhere to such substrate, forming a strong
mechanical bond. The an electrical arc or discharge 8 can be
produced from the distal end of the electrode 2 using such
exemplary one-sided electrode apparatus 100, even if the distal end
of the electrode 2 is not proximate to an electrically grounded
object. Thus, an electrical arc or discharge 8 may be produced in
proximity to electrically nonconductive substrates, in contrast to
conventional arc welding systems and the like. The distal end may
be placed at an optimum distance in order to enhance the amount of
bulk property change. For example if a large kinetic energy from
the particle is required then the end may be placed in a fashion
aligned with gravity to enhance the kinetic energy. This kinetic
energy may be later transformed into a thermodynamic static
potential. Energy interactions by particle chemical interactions
and with the substrate or atmosphere are possible
[0044] A further exemplary apparatus 200 is shown in FIG. 2 which
can be used to provide a bulk modifying coating on a large
substrate 12. Such exemplary apparatus 200 can include a deposition
arrangement 16, which may be configured to produce an electrical
arc or discharge 8 and emit ionic or other particles 9. The
deposition arrangement 16 can be affixed to a translating
arrangement 17, which can controllably move the deposition
arrangement 16, e.g., along or over at least a portion of a large
substrate 12. Thus, particles 9 can be deposited on a large
substrate to form a coating thereon. The translating arrangement 17
can include or communicate with a controller (not shown) which can
control the position and/or speed of the deposition arrangement 16
relative to the substrate 12. Thus, the location and amount of
deposited coating formed by the particles 9 can be controlled. For
example, such controller can control a position of the distal end
of the electrode 8 relative to the substrate 12, e.g., provide a
substantially constant distance between them, which can further
allow a more uniform deposition of particles 9 on the substrate 12
as well as influence the bulk properties.
[0045] A still further exemplary apparatus 300 which can be used to
provide a bulk modifying coating which is interactive with the bulk
is shown in FIG. 3. Such exemplary apparatus 300 can include the
deposition arrangement 16, which (as described above) may be
configured to emit particles 9. The deposition arrangement 16 can
be provided at least partially inside an enclosure (chamber) 19,
and the enclosure 19 can further enclose an object 21 to be coated
with a bulk modifying coating. Using this exemplary apparatus 300,
the particles 9 can be deposited on an object 20 to form a coating
thereon. Further, any of the particles 9 which are not deposited on
the object 21 may coat the enclosure 19 or remain unattached in the
enclosure. This exemplary configuration can assist in recovering
such particle material, which may be then be reused or recycled.
The belt 21 can be coated. Masking of specific objects can be
carried out by standard masking techniques such that only selected
area receive the bulk modifying coating
[0046] Yet another exemplary apparatus 400 which can be used to
provide a coating is shown in FIG. 4. Such exemplary apparatus 400
can again include the deposition arrangement 16, which is
configured to emit the particles 9. The deposition arrangement 16
can be provided in proximity to a conveyor belt 20 or similar
transport apparatus. A plurality of objects 21 to be coated with a
bulk modifying coating can be provided on the conveyor belt 20.
Using this exemplary apparatus 400, particles 9 can be continuously
deposited on a large number of objects 21 to form a coating
thereon. A mask is shown 22 which can be used for selective
coating. System parameters, such as speed of the conveyor belt 20
and intensity of discharged particles 9, area of the mask, may be
adjusted to provide a suitable amount or thickness of the coating
on the objects 21. Multiple passes with different mask locations is
possible.
[0047] In further exemplary embodiments of the present invention,
the electrode 2 can have a form of a wire that may be continuously
fed as it is consumed to form particles. The wire may take the form
of a coil which can be inserted or retracted from the inside of a
long hollow tube 12. A control arrangement can be provided which
includes, e.g., a feedback arrangement to control the speed at
which such wire is fed, and which can preferably maintain a
substantially constant distance between the distal end of such wire
electrode 2 and the substrate being coated. Such control
arrangement can be based, e.g., on mechanical, optical, electrical,
or thermal sensors. The voltage provided by generator 1 and the
diameter of the electrode 2 may also be controlled to provide
desired particle sizes. For example, thinner electrodes and/or
higher voltages may produce smaller particle sizes.
[0048] According to still further exemplary embodiments of the
present invention, a plurality of electrodes 2 may be used, where
different ones of the electrodes 2 may have different compositions
and/or diameters to provide particular desired properties in the
deposited coatings. Such electrodes 2 may be provided with
electrical power to generate a discharge either simultaneously or
sequentially as the distal ends of the electrodes 2 are moved over
the substrate. Different electrical frequencies can be applied to
the different electrodes 2, and distal ends of such electrodes may
also be provided at different distances from the substrate being
coated. Alternatively, a varying electrical frequency may be
applied to a single electrode 2 to produce variations in particle
sizes and/or other properties in deposited coatings. For example,
coatings having a range of compositions, compositional gradients,
and/or coatings with a plurality of layers can be created using a
plurality of such electrodes 2.
[0049] In yet further exemplary embodiments of the present
invention, a coating material may be provided on a substrate using
a one or more single-sided electrode arrangement 100 similar to one
shown in FIG. 1. The electrode 2 may have a form of a rod or wire,
and can be electrically conductive or semi conductive or partially
non conductive. A material or coating may be produced by providing
an ionized discharge 8 (e.g., an electrical arc) at a distal end of
the electrode 2, and placing a substrate to be coated in proximity
to the discharge 8. The discharge 8 may be continuous, and it can
be formed in the absence of a nearby object that is electrically
grounded. The particles 9 produced by an interaction between the
discharge 8 and the material of the electrode 2 can impinge on the
nearby substrate and adhere thereto as well as influence bulk
properties such as thermal conductivity. Vacancies and
disclocations/disclinations may be generated or modified. Defects
such as porosities, grain-boundaries, interface boundaries and
cracks may change shape or blunt or be deflected or transported. It
is recognized that all of these defects can have several variations
such as a Schotky or Frenkel defect in an ionic material which is a
variation of a vacancy but with charge issues.
[0050] The particles 9 which may be used to form the coating may
have an average size that is less than about 1000 nm, less than
about 800 nm, or preferably less than about 500 nm, or more
preferably less than about 200 nm. As will be noted in the
embodiments discussed below nano particles appear to be best suited
for the invention. The particles 9 may have a shape that is
approximately, spherical, cylindrical, acicular, or a mixture of
these geometries. The small particles 9 which can form the coating
can be unsintered or only partially sintered, and may retain an
open porous structure even at high temperatures. The particles 9
can also remain adherent to the substrate and may resist further
densification and pore closure even at high temperatures (e.g.,
about half of the absolute melting temperature of the substrate or
a constituent thereof). The coating may further be resistant to
wear or removal from the substrate under a range of conditions,
e.g., rubbed or abraded against other objects, washed or otherwise
cleaned, exposed to chemicals and solvents, etc. The particle and
substrate may create conditions for bulk property changes. The
surface area density of the surface coated with small particles may
be approximately 2 to 10. The coating density could be a measure of
the efficacy for bulk modification by the particles. In particular
a lower density may offer high modification ability in some cases
but not always. The particles or jointly with the substrate or film
may have a glassy component. Composite particles and substrates are
envisaged including glassy components, fibrous components and
discreet or continuous components. In fact the use of angular
glassy particles may be preferable or diamond particles with
facets. It is thought that the interactive nature of the coating is
important. Further it is thought that the interactive nature of the
film, coating and surface of the substrate is also important in
order to see substantial bulk modifications.
[0051] The grain boundary structure, dislocations or chemistry in
the bulk region now modified by the coating especially under the
bulk regions close to the substrate coating interface can be
modified thus leading to a change in properties. For example high
dislocation density boundaries may form replacing low angle
boundaries or sessile dislocations may replace glissile
dislocations. These terms are commonly understood in the materials
literature. When nano particles especially less than 20 nm are
employed for the coating it is likely that some may be trapped in
defect sites including, pores and grain boundaries. It is also
possible that there is a time and/or temperature dependence to the
evolution of changed properties in the bulk i.e. the property
development or changes may occur over a time period especially
under a stress environment. Cold work that was trapped in the bulk
because of the coating may recover or aid recrystallization whether
static or dynamic. Again these are terms commonly known in the
materials literature. The modification to the grain boundary may be
through compositional reasons or stress (including stress
cyclicity), defect creation or modification or recrystallization or
grain growth.
[0052] The electrode 2 may be used to generate particles 9, which
may then form at least a portion of the materials. For example,
deposition of particles 9 may produce combinations and/or mixtures
of the above-mentioned elements and/or compounds during deposition
on a substrate. Such compounds and mixtures may include further
compounds which can result from reactions of the particles 9 with,
e.g., moisture, oxygen and/or nitrogen from surrounding air or
deliberately introduced gases during deposition. For example,
particles containing defect structure oxycarbonitrides could be
formed and deposited on the substrate. Some of the substrates
studied to provide examples of the invention are the three metallic
alloys for boiler tube materials including two steels (T92 and
S304H) and one nickel base super alloy (CCA617) that are listed in
Table 1. The nominal chemical composition of these alloy tubes are
given in Table 1. Other substrates examples by way of non metallic
materials include polycarbonate, Polyethylene (HDPE and LDPE),
Teflon, chlorine, carbon, fluorine and nitrogen polymers and
biological materials, Polypropylene (PP), Polystyrene (PS),
Polyvinyl Chloride (PVC), Polyethylene Terephthalate (PETO) and
other common plastics used in for engineering articles. Porous
materials including porous ceramics of alumina, silica, titanates,
barium titanate, glass, diamond, silicon carbide, molysilicide and
carbon, were also used as substrates or used as particles.
TABLE-US-00001 TABLE 1 Composition of boiler steels and Ni base
alloy by weight percent (nominal) Element, Wt % T92 Ferritic Steel
S304H Steel CCA617 Super alloy C 0.07 0.10 0.05 Cr 9.0 18.0 21.7 Ni
-- 9.0 55.0 Fe Remainder Remainder 0.6 Co -- -- 11.25 Mo 0.5 -- 8.6
Al -- -- 1.25 W 1.8 -- -- Mn 0.45 0.80 0.03 Si 0.03 0.20 0.10 N
0.06 0.10 0.01 V 0.2 -- -- Nb 0.05 0.40 -- B 0.004 -- 0.002 Cu --
3.0 0.01 Ti -- -- 0.4
[0053] Magnified views of exemplary coatings deposited on
substrates in accordance with exemplary embodiments of the present
invention are shown in FIGS. 5-10. FIG. 5 shows a coating on a
plastic. Bulk cracks may be sipped or deflected by the particles
and influence the bulk properties as noted from micro structural
features in FIG. 5 and FIG. 10. Another example, FIG. 6 shows a
backscattered secondary electron image ("SEM") image of a coating
material containing silicon. The dark region on the very top is the
mounting material. Under that is the coating with fine .about.50 nm
particles, below that is what is thought to be a high cold work
region in the bulk and far below that is a seemingly unmodified
material. The coating was applied in this embodiment to a stainless
steel surface alloy 304H. An exemplary SEM image of silica
nanoscale particles which were deposited on a CCA617 substrate in
accordance with exemplary embodiments of the present invention is
shown in FIG. 7. In this case the coating is less than 300 nm
thick.
[0054] FIG. 7 is an exemplary scanning electron microscope ("SEM")
image of small particles containing silicon (thought to be glassy)
which were deposited on a stainless steel substrate. Such particles
have been observed to be strongly adherent to the substrate, and
did not rub off even when applying mechanical shear. The mounting
(Bakelite) is the black part above the tin coating. Note in
particular the bulk modification which extends to over a micron
i.e. about 500% more than the coating thickness.
[0055] FIG. 8 is an exemplary SEM image of particles which were
deposited on a T92 alloy. Note again that the bulk microstructure
is influenced. Such particles have been observed to be strongly
adherent to the substrate, and did not rub off even when applying
mechanical shear. The mounting (Bakelite) is the black part above
the tin coating. Note in particular the bulk modification extended
to over a micron i.e. about 500% more than the coating
thickness.
[0056] Coatings may be made on metals, ceramics, polymers,
composites etc. for beneficial property enhancements. FIG. 5 and
FIG. 10 in particular shows crack travel modification in the bulk
by the particles. FIG. 9 is an exemplary SEM image of particles on
and in the substrate after a very heavy dose of coating. FIG. 10 is
an exemplary SEM image of particles on and in the substrate after a
light dose of coating. FIG. 11 is an exemplary image showing
regions of a coating where particles which are either connected in
a region or are individually attached to the substrate.
[0057] The small particles, which may be microscopic or nanoscale
(e.g., having an average size that is less than about one micron),
can be deposited as one or more layers on a substrate. Preferably,
such deposited particles will not be in a substantially sintered
condition, e.g., they may still exhibit a degree of porosity after
being deposited on a substrate. A cross sectional view of such a
porous coating was shown in FIG. 8. For some of substrates which
are porous or soft, like polymeric materials (plastics) the
delineation between the coating and original substrate is not like
shown above but extends further into the substrate surface i.e.
into the bulk and thus modifies the bulk also by particle
incorporation.
[0058] Exemplary durable materials in accordance with exemplary
embodiments of the present invention can be created using the
exemplary apparatus shown in FIG. 1. For example, a commercial
generator 1 may be used which provides alternating current at
approximately 14 MHz from a 120 volt, single phase input. Such
generator can be provided in electrical contact with one side of a
conventional Pi circuit (e.g., inductive coil 3 and capacitors 4,
5, 6). For example, the coil 3 may have a diameter of several
inches (e.g., between about 2 inches and 6 inches), and the
capacitors 4, 5, 6 can have a capacitance value of between about 30
picofarads and about 100 picofarads. The Pi circuit may include
such components (e.g., coil 3 and capacitors 4, 5, 6) which may
have values that lie outside these approximate ranges. The other
side of the Pi circuit can be provided in electrical contact with
one or more electrodes 2. Such electrodes 2 can be, e.g., wires
which contain one or more particular compositions that can be used
to form the exemplary coatings described herein.
[0059] When the generator 1 is powered, the distal end of the
electrode 2 may be provided a few inches away from the substrate to
be coated. For example, a distance of a between about 1 inch and
about 6 inches can be used, or preferably a distance of about 3-4
inches. Other distances may be used depending on the amount of
power supplied, the diameter and material of the electrode, etc.
The distal end of the electrode can be passed over a portion of the
substrate to cover a particular area thereof with the exemplary
bulk modifying coating. A substrate exposure time of several
seconds (e.g., about 1-10 seconds) may be sufficient to form such
exemplary coating on the substrate. The exposure time can
represent, e.g., a duration of time in which power is provided to
emit particles from an electrode that is stationary relative to a
substrate, or a duration of time in which particles from an
electrode are provided onto a particular portion of a substrate,
where the electrode and substrate are in relative motion to each
other. Such residence time can be increased, e.g., by providing
multiple passes of an electrode over a particular portion of a
substrate. Such multiple passes using at least two different
electrodes on different passes (or using one electrode supplied
with electrical energy having different characteristics such as,
e.g., frequency for different passes) may be used to create
multilayered coatings which can include a plurality of layers
having different compositions, particle sizes, or other
properties.
[0060] The particles formed from the electrode, which may be
deposited on the substrate to form an coating, may preferably have
a size on the order of a few hundred nanometers or less. For
example, the average particle size may be less than about 1000 nm,
less than about 800 nm, preferably less than about 500 nm, or more
preferably less than about 200 nm. Smaller electrode diameters may
be used to form smaller particles. For example, an electrode having
a diameter of about 1 mm or less can be used to form particles
having a size of a few hundred nm or less. Several such thin
electrodes may be provided in proximity to each other to cover a
larger area of a substrate more quickly and/or uniformly.
[0061] The coating formed on the substrate can be very thin, e.g.,
on the order of several particle layers or less (see e.g. FIG. 7).
Thick or thin coatings may be preferable depending on the
application and cost, i.e. with respect to cost, durability,
formation time, etc. For example, exemplary coatings can have a
thickness that is less than about 2000 nm, or preferably less than
about 1000 nm in certain boiler or capacitor applications. In
certain exemplary embodiments of the present invention, the coating
thickness can be less than about 800 nm, or less than about 500 nm,
or even less than about 250 nm. The exemplary particle and coating
dimensions described herein can provide coatings which may be very
durable and firmly adherent to the substrate or to each other. It
is by now well known that very small nano particles may exhibit
unusual properties. However the present invention deals with
coatings that influence bulk properties. Several of the precise
relationships between the nanomaterial and coating thickness which
impact the bulk properties are relatively unknown to us at this
time however we anticipate that unusual affects of nanocoatings
especially comprising nano particles under 50 nm or more preferably
20 nm. We anticipate that benefits of the particle to the bulk may
not always manifest completely only during the initial coating
application but could be mainly manifested subsequently as can be
noted in some of the examples below which discuss bulk
microstructure modifications, (which are a way of inferring changes
in the bulk property differences), when observed without the
coatings and compared with the presence of the adherent coating
during a similar air or steam oxidation exposure.
[0062] All previously identified electrodes materials and shapes
that may be used in accordance with PCT/US2006/060621 and
PCT/US2007/085564 and U.S. patent application Ser. No. 11/098,474
are fully incorporated by reference. Exemplary coatings which
include nonconductive materials may be formed in several ways. For
example, a nonconductive thin rod or fiber may be covered with a
conductive material to provide such electrode or vice-a-versa. In
one exemplary embodiment, a silica fiber provided with a metallic
coating (e.g., silver, tungsten, or iron) may be used as an
exemplary electrode. Alternatively, one or more nonconductive rods
or fibers may be provided adjacent to one or more conductive rods
or fibers. A discharge formed at the distal end of a conductive rod
or fiber as described herein can produce particles of both the
conductive and nonconductive materials, which may then be deposited
together on a substrate to form a coating in accordance with
certain exemplary embodiments of the present invention. Electrical
conductivity of such materials may change when deposited. For
example, conductive oxide electrodes may gain oxygen during
deposition and become nonconducting after being deposited. In
certain exemplary embodiments of the present invention, a plurality
of layers may be sequentially deposited using electrodes having
different compositions, where certain layers may be conductive and
others may be nonconductive. In this manner, materials exhibiting a
variety of dielectric properties can be provided.
[0063] Two or more layers of particles may also be deposited on a
substrate to form a coating containing particles of more than one
composition. For example, a first deposition may be applied to a
substrate using a first electrode having a first composition, and a
second deposition may then be applied to the substrate using a
second electrode having a second composition. Between the several
depositions the new substrate surface and new bulk properties could
be modified further by heat treatment or chemical reaction
including cleaning. This procedure can be further repeated if
desired to improve not only surface properties but also bulk. Bulk
property enhancement is considered to be anywhere in the non
coating part of the structure. In this exemplary manner, a coating
containing particles having different compositions may thus be
provided for enhancing different bulk properties. Exemplary
coatings may not have the same composition as the initial starting
material of the electrode(s) used to form them. For example,
non-stoichiometric particles and other compounds may be produced
during formation of such exemplary coatings by reaction of the
starting materials with each other and/or with ambient substances
such as, e.g., oxygen, nitrogen, carbon-containing gases, or
moisture.
[0064] A combination of metallic and oxide particles may further be
used as a coating such as, e.g., a coating containing Si, Al, Mo
and SiO2. An oxide which forms in such exemplary coatings may be
dispersed as separate particles within the coating or the coating
and substrate structure. Alternatively, a surface of certain
particles may oxidize while the interior of such particles may
remain metallic. The oxide formed can be porous or non porous. Such
oxides may be intentionally formed or enhanced, e.g., by exposing
metal-containing coatings to an oxidizing atmosphere after they are
deposited, optionally with simultaneous heating of the coatings.
Such oxidation may also occur spontaneously in such coatings, e.g.,
during application or use. Alternatively, deposited coatings may be
subjected to a reducing treatment after they are deposited on a
substrate. The bulk may thus be influence in manner to change its
properties by interaction between the substrate surface, the
coating and the environment.
[0065] Exemplary embodiments of the present invention may be used
to coat various objects with coatings in situ. For example, the
exemplary apparatus described herein and shown, e.g., in FIG. 1,
may not require any electrical grounding of the substrate. Thus,
exemplary structures may be applied to a variety of objects,
including nonconductive objects, without relocation or removal of
the object. For example, common objects such as boilers components,
common plastics, may be coated simply by providing an electrode
having a discharge as described herein in proximity to the object.
If the bulk properties of a coated object somehow diminish over
time, they can be `rejuvenated` by reapplying a coating of the
material as described herein. Cracks that develop in boiler or heat
exchanger materials during use may be healed while simultaneously
improving the bulk properties. In some applications the coating
could dramatically influence the overall oxidation of the materials
for example in hot air or air and steam and/or more generally when
reacted with an environment or object with a film or by itself. In
such instances the benefit of the particle to the bulk may not
manifest completely fully during the initial coating but could be
noted with time as may be noted in some of the examples shown below
which discuss bulk microstructure modification differences when
observed without coatings and when observed with coating during a
similar air or steam oxidation exposure. Hole creation or creation
of passages in the bulk is enabled by the invention. One such
example can be noted in FIG. 9.
[0066] In several of the examples discussed below the change in
properties whether instantaneous or over time may be more than two
times if the particles were not present.
Examples
[0067] Weight change measured during the steam oxidation up to 100
hours is shown in FIGS. 12, 13, and 14 for the CCA617, S304H, and
T92 steel, respectively with and without a particulate coating of
this invention (see FIGS. 5-10). Note that for all the alloys the
nanostructured coated coupons did not show any significant weight
change (similar results were obtained for air oxidation). The error
bars indicate the possible experimental error or measurement error
reflecting the maximum sensitivity of the weighing machine.
Differences in oxide thicknesses or films reflect differences in at
least one constituent from the substrate and this influence also
the bulk properties in such a manner.
[0068] SEM/EDS confirmed the presence of Mo, Si, Al and O in the
coating. SEM micrographs of the surfaces and polished
cross-sections of the uncoated and coated coupons of CCA617,
Super304H and T92 steel that were subjected to steam oxidation for
100 hours are shown in FIGS. 15, 16 and 17 respectively. An oxide
scale was observed in all cases. The very black part on top of the
cross-section micrographs is the mount (Bakelite). Thus the
structure initially applied can include for example a
bulk-encompassing film of silicon oxides or alumina or chromia
(i.e. binary or higher order of oxides of aluminum or chromium or
combinations) which are all understood to form either during the
coating process or during further exposure to temperature in air or
other environments. These films which may or may not include the
oxides can be crystalline or glassy or combined but are seen to be
different in some manner, including size. As the films are a part
of the bulk either from the initial state or during further
exposure they are considered to finally become bulk regions which
are modified by the coating. Note again that the bulk region is
thicker than the coating plus the immediate substrate surface. SE
is the secondary electron image and BSE is the Back scattered
electron image.
[0069] The coated CCA 617 sample revealed a thinner oxide scale
(.about.1 .mu.m) compared with the counterpart uncoated sample
(FIG. 12). Analysis of the peaks in XRD spectra recorded from the
oxidized surface indicated the presence of Cr.sub.2O.sub.3,
together with the FCC matrix underneath in both samples. Analysis
of EDS spectra recorded from the surface and cross-section
confirmed the presence of the Cr.sub.2O.sub.3 oxide scale. Modest
levels of Si were also present in the oxide scale in the nano
coated sample. In addition, the presence of thin films of an
Al-rich oxide (dark in contrast) was noted along the grain
boundaries in the cross-section samples. Some of the oxides were
present to a greater extent and deeper into the substrate in the
uncoated coupons. Again the particulate coatings are thus thought
to have modified the bulk structure differently when compared to an
uncoated object given the same thermal or environmental treatment
of the substrate but without the coating
[0070] The difference was also observed for a stainless steel
substrate. The oxide scale on the coated Super304H sample was
thinner in the nanoparticle coated samples compared with the
counterpart uncoated sample (FIG. 15). XRD analysis of the oxidized
surface revealed the presence of Cr.sub.2O.sub.3, (Fe, Mn,
Cr)O.sub.4 and the fcc matrix in both samples, which was also
confirmed by EDS in the SEM. Often XRD analysis is unable to pick
up the subtle but important differences, the microstructures and
thicknesses were different as is noted. A combination of several
analytical techniques may be required to identify the differences.
Films are identified in the micrographs and may or may not
correspond to the oxide. SEM micrographs of steam oxidized T92
steel both coated and uncoated are shown in FIGS. 17a and 17b,
respectively. The nano-coated steel has a fine scale oxide
distribution (FIG. 17a) compared with the coarse oxides noted (FIG.
17b) in the uncoated steel. The cross-section samples also reveal
that the oxide scale in the nano-coated sample is substantially
thinner (1-2 .mu.m) than that in the uncoated sample (.about.100
.mu.m). One set of coated and uncoated tube coupons were subjected
to the Static Air Oxidation for 500 hours. Another set of tube
coupons was oxidized for 1000 hours. The word static is used to
represent that these coupons were stationery for the full 500 or
1000 hours inside the furnace at the oxidizing temperature. The
weight change after 500 hours of oxidation in the box furnace for
the coated and uncoated tube coupons of the CCA 617, S304H, and T92
steel are given in the Table 2, and a corresponding bar chart is
shown in FIG. 18.
TABLE-US-00002 TABLE 2 Summary results of 500 hour Static Air
Oxidation Temperature Time of Coated or of Oxidation, Oxidation,
Weight change, Alloy Uncoated .degree. C. Hours mg/cm.sup.2 CCA617
Coated 700 500 0.1102 Uncoated 700 500 0.2357 S304H Coated 700 500
0.0000 Uncoated 700 500 0.2461 T92 Coated 650 500 0.0000 Uncoated
650 500 0.2412
[0071] One set of coated and uncoated tube coupons of the CCA617,
S304H, and T92 steel were subjected to static air oxidation in a
box furnace for 1000 hours in a single cycle. The weight change
data is given in Table 3, and the corresponding bar chart is shown
in FIG. 19.
TABLE-US-00003 TABLE 3 Summary 1000 hour Static Air Oxidation
Temperature Time of Coated or of Oxidation, Oxidation, Weight
change, Alloy Uncoated .degree. C. Hours mg/cm.sup.2 CCA617 Coated
700 1000 0.1159 Uncoated 700 1000 0.2379 S304H Coated 700 1000
0.0000 Uncoated 700 1000 0.3656 T92 Coated 650 1000 0.0000 Uncoated
650 1000 0.2235
[0072] SEM micrographs of the coated and uncoated samples of the
CCA617, Super304H and T92 steel oxidized for 500 hours and 1000
hours are shown in FIGS. 20 through 23.
[0073] The coated CCA 617 sample revealed a thinner oxide scale
(.about.0.5-1 .mu.n) compared with the counterpart uncoated (3-5
.mu.m) sample (FIGS. 20 and 21). An analysis of the peaks in XRD
spectra recorded from the oxidized surface indicated the presence
of Cr.sub.2O.sub.3, together with the FCC matrix underneath in both
samples. Analysis of EDS spectra recorded from the surface and
cross-section confirmed the presence of the Cr.sub.2O.sub.3 oxide
scale. Modest levels of Si were also present in the oxide scale in
the nanoparticle coated coupon. In addition, the presence of
particles of an Al-rich oxide (dark in contrast) was noted along
the grain boundaries in the cross-section samples (FIGS. 20, 21).
These oxides were present to a greater extent and deeper into the
substrate in the uncoated coupons (FIGS. 19b and 20b). Longer time
exposure to 1000 hours did not cause much thickening of the oxide
scale in the nanoparticle-coated sample compared with the
counterpart uncoated sample (FIG. 20). This experiment is another
embodiment which shows that the bulk structure is influenced
differently between coated and uncoated materials because of the
presence of the coating and substrate.
[0074] SEM micrographs of the coated and uncoated T92 alloy samples
oxidized in air at 650.degree. C. for 1000 hours are shown in FIG.
22 (a) and (b). The oxide layer was quite thin in the
nanoparticle-coated sample but also thinner than that in the
uncoated sample. In this embodiment the particulate coating is also
enabled by the oxidation process following a first application of a
particulate coating. Note again clearly the bulk differences for
the depth of the micrograph between FIG. 22(a) and (b).
[0075] In the case of a special stainless steel, Super304H the film
was thinner in the nano particle coated material compared to
uncoated. XRD analysis of the oxidized surface revealed the
presence of Cr.sub.2O.sub.3, (Fe, Mn, Cr)O.sub.4.
[0076] An indication of the long duration of bulk property
differences between objects with the invention and objects without
the invention was noted even after 3000 hr tests. In one embodiment
it was noted that nanoparticles (of average particle size less than
150 nm) comprising a coating of nanothickness (less than 1000 nm)
for a object made of a Fe--Cr--Al alloy, displayed enhanced erosion
resistance even after 3000 hrs of use in a combustion-gas flow
environment when compared to an uncoated article. The erosion
resistance was unanticipated because the nano coating would have
been expected to possibly loose its efficacy much sooner if only
the surface wear of the coating or only substrate surface is
considered. However, it appears that because regions of the bulk
were strengthened against erosion from the combustion particulate
matter and reactive hot gases, even after thousands of hours of
harsh testing. Although erosion is a surface deterioration
phenomena, we associate the long time benefits of erosion to be
reflective of the change in bulk properties at least in some
regions of the substrate interior to the initial surface on which
the particulate coating was applied. A surface is a two dimensional
entity and bulk refers to a three dimensional entity even when the
third dimension is small e.g. greater than the thickness of the
coating preferably greater than two times the thickness of the
coating.
[0077] In further exemplary embodiments of the present invention,
rough or defective surfaces or objects may be treated by filling
cracks, crevices and/or pores with materials using the exemplary
method and apparatus described herein. Alternatively, modified
materials may be provided using the exemplary apparatus, method,
and compositions described herein in order to obtain beneficial
results.
[0078] Having thus described in detail preferred embodiments of the
present invention, it is to be understood that the invention
defined by the appended claims is not to be limited to particular
details set forth in the above description, as many apparent
variations thereof are possible which lie within the scope of the
present invention as recited in the appended claims. Certain
modifications and variations of the method, apparatus, and
compositions described herein will be obvious to those skilled in
the art, and are intended to be encompassed by the following
claims.
[0079] When referring to the claims below it is obvious that the
chemical nature or size of the coating particles, or the coating
process are all encompassed by a reference to a bulk modifying
coating. This is in-line with the commonly held knowledge where a
process and composition both influence the microstructure and hence
properties of a material.
* * * * *